1. Field of the Invention
The present invention relates to a radial lead type inductor to be used as a power choke coil, for example, in various electronic appliances.
2. Description of the Related Technology
A radial lead type inductor to be used as a power choke coil, for example, in a consumer electronic appliance or an industrial electronic appliance has a wire including a copper wire insulated with polyurethane, which is wound about a scroll of a drum core. The beginning and end of the wound wire are led in parallel from lead sections such as grooves and holes, which are spaced apart with a predetermined pitch, in one collar of the drum core and are fixed to the lead sections with an adhesive. The beginning and end of the led wire are used as lead terminals by removing the insulating coating. In the radial lead type inductor, the lead terminals are inserted to lead inserting holes in a circuit substrate of various electronic appliances and are conductively connected to a land electrode partially in a wiring pattern of the circuit substrate by flow soldering to implement. More specifically, as disclosed in JP-UM-A-2-76804, a drum core has two semicircular grooves, which face against each other and fix coil ends, on the outer circumference of a flange part, and a wire is wound between a pair of collars of the drum core, and the ends of the wire extend along the grooves.
In recent years, the reduction of power consumption in electronic appliances is strongly needed, and there has been a strong tendency to provide an inductor for use in a power supply circuit having a desired inductance value, which is optimum for a circuit.
However, in a radial lead type inductor as in the related art, as a part is shown in FIG. 7, the beginning 105a and end 105b of a wire 105 are led to a drum core 101, and a pair of grooves 106a and 106a of one collar 103 of the drum core 101 are placed against each other at positions displaced 0.5 T (turn) about the axial center of the drum core 101. For this reason, in the radial lead type inductor 100 having a smaller inductance value since the number of layer of the wire 105 wound about the drum core 101 is one or below, the number of turns of the wire 105 wound about the drum core 101 is in blocks of 1.0 T, such as 5.5 T, 6.5 T and 7.5 T. Therefore, the inductance value of the radial lead type inductor 100 is equal to the step width, which is equivalent to 1.0 T of the wire, and it is difficult to meet the need.
As disclosed in JP-UM-A-2-76804, the positions of the grooves 106 may be changed in accordance with the number of turns of the wire wound about the drum core 101. However, in this case, the changed pitch is different from a standard lead pitch used for a radial lead type electronic part automatic inserting apparatus to be used for installing the radial lead type inductor onto a circuit substrate, and the automatic inserting apparatus is no longer usable, which is a problem.